It's the action's job to take biz objects from the service and convert them (if necessary) for display on the screen, and take data from the jsp and convert it to biz objects to send to the service. An action should do only one thing, i.e. we aren't doing actions the "multiple method" way.
For apps that use SAP, all your actions should be subclasses of SAPBaseAction. It will stop any time a rfc call results in an Exception. In the rare case you need to do something else (like continue other processing) when an Exception is encountered, you can wrap a try catch on MessageRuntimeException around your service execute calls.
This provides automatic RFC error message handling (i.e. it takes all rfc messages and stores them into the struts actionmessages automatically).